well, here goes my first pass at an answer. kind of stream of consciousness, so bear with me.
first, my definition of morality. as usual, i express a somewhat simplified perspective. i like simple. i leave the more philosophical, abstract perspectives to those who prefer that approach.
morality is, at its most basic, a belief in a particular set of values that determine what is right and what is wrong; a doctrine for correct and incorrect behavior (and thought?). the specific values may be different depending on the authority that defines them; what remains the same is the fact that those values are intended to apply to all. while it may be possible to argue that this can be applied at the individual level, in practice that seems to be an idealistic anachronism. in my 54 years of experience in this world, morality is invariably a belief in a particular set of values determining what is right and wrong *for everyone*.
moralism, as best i can define it, is just the tendency to use morality for one's own purposes, be they political, strategic, propogandistic, patronizing, etc.
so, what are my arguments against morality?
first and foremost, morality as i see it has absolutely *no* allowance for, or acknowledgement of, context. it defines itself in completely black and white, binary terms. the doctrine is defined by some authority, and it is supposed to apply to everyone at all times. (i guess there is an argument that when morality is applied to those in power, by those in power, context does in fact play a role.)
at the highest level, now that i think of it, that may be my *only* argument against morality. everything else may simply stem from that primal objection.
i guess there is also the fact that any morality (that i see as such) is defined by some authority, typically an institutional authority at that. so epic fail on that count, as an anarchist.
the very words "right" and "wrong" have moralistic overtones for me. it is difficult to avoid them completely, just given their ubiquitous usage in every aspect of life. but conceptually, i think more in terms of what works for me and what doesn't; what is desirable and what is not. i cannot possibly know what is right or wrong (or desirable/undesirable) for others, much less for *everyone*. in certain situations i may be able to make an educated guess what works or not for someone that i know well, but even that is constantly challenged.
of course, my conscious behavior is (typically) viscerally informed by some set of constantly evolving (*major* point there) guidelines, in pursuit of fulfilling my needs and desires.
take, for example, stealing (leaving aside the whole "property is theft" and "reappropriation" discussion for now). i do it, and not infrequently. yet, i do not steal from people i care about. some would say "it is ok to steal from walmart, but not from joe's local hardware store." i don't see it quite that cut and dried. joe's may be a small, family business. but joe may be an asshole that abuses his employees, or otherwise does shit i hate. my general guideline there is: anyone that tries to profit from selling me something i need is a potential victim of my skills. if it is someone i care about, i am unlikely to steal it from them, especially if i know they need the money they take in by selling that item. if i can afford it, i will pay them for it; otherwise i will try to steal it elsewhere. ultimately, if i can do neither, i will try to work something out with them (barter, gift, etc). none of that is rooted in any morality; it is rooted in my desires for freedom and control of my own life, which includes those relationships that are meaningful to me. by the same token, the only reason i don't focus on stealing from banks is the likelihood of my being incarcerated as a result, since i do not have the skills i deem necessary to get away with it. it is surely not some moral aversion to that behavior.
i may have more to add, but that's all that flowed out for now...
[edited to add a point]